Sensitization of photographic emulsions



Patented May 11, 1937 v UNITED STATES PATENT OFFICE SENSITIZATION F PHOTOGRAPHIO EMULSIONS John David Kendall, Ili'ord, England, assignor to Ilford Limited, Ilford, England, a British com- Britain August 3, 1934 '7 Claims.

This application corresponds to the applica-' tions of John David Kendall, Serial No. 22,727/34, filed 3rd August, 1934 and divisional application Serial No. 6314/36, dated 3rd August,

1934, which were both filed in Great Britain, and is a divisional of United States application Serial No. 76,703, filed 27th April, 1936.

This invention relates to the sensitization of photographic silver halide emulsions by incorporating in the emulsion a dye or dyes which have the property of extending the range of spectral sensitivity of the emulsion.

It is well known that the cyanine dyes, that is dyes comprising two heterocyclic nitrogen is nuclei joined by a methine or polymethine chain, modify the spectral sensitivity of silver halide emulsions.

In the specification of my co-pending application No. 76,703' filed 27th April, 1936 (from which this application is divided) I have described the preparation of dyes having a structure similar to that of the cyanine dyes but containing one or two nitrogen atoms in the linking chain between the two heterocyclic nuclei. 1 have found that when such dyes are alkyl salts, and so contain a quinquevalent nitrogen atom linked to a trivalent nitrogen atom by a completely conjugate chain. they have the property of extending the spectral sensitivity of silver halide emulsions.

In a paper in J. C. S. volume l25, (1924) page 1348, Dr. Hamer describes the preparation of l: 1-dimethyl-2:2'-azocyanine idodide and states that a solution of this compound is pale yellow with a blue fluorescence and is unlike the cyanines in that it is not decolorized by acids whilst it has no action on a photographic plate. I have found that l 1 -dimethyl-2 2'-azocyanine iodide is a powerful sensitizer for silver halide emulsions, particularly for silver chloride emulsions and it extends the sensitivity of a silver chloride emulsion to A 4500 A. with sharp maxima at about A disc A. and i 4400 A. This compound is one of the class of compounds which I havenow found to have sensitizing properties and I include its use as a sen'sitizer in the appended claims. 4

' According to my invention a method of extending the spectral sensitivity of photographic silver halide emulsions (particularly silver chloi ride'einulsions) comprisestreating the emulsion 5 with "a compound containing two heterocyclic nitrogen nuclei (one of which contains a trii valent and .the other a quinquevalent nitrogen atom). which are'lin in the a or 7 positions all to the nitrogen atoms by a linkage selected from the group consisting of N=, -CH=CH--N=, N=CHN= or N=CXN= (X representing a hydrocarbon group).

The invention also includes a photographic 5 silver halide emulsion containing one of the above-mentioned compounds.

In carrying out my invention I find that it is preferable to use the compounds containing the chain --CH=CHN= when it is desired to 10 extend the spectral sensitivity of a silver bromide or iodobromide emulsion.

The class of compounds which may be employed in accordance with the invention is illustrated by the following typical examples; 15

S h t a N/ N v and other heterocyclic ring compounds containing two nitrogen atoms in the same ring, as described in British Patent No. 425,609) and their homologues in the benzene, naphthalene and homologous series, and the nuclei attached to 5 the ends of the; chain may be different from one another, but in the case of the compounds having the linkage -N=CHN= the nuclei will normally be. the same.

The sensitizing action-of the dyes which may be used in accordance with the present invention is illustrated by the following typical examples of compounds which may be employed. These examplesare merely given as an illustration of the type of compound which may be em- 'ployed. I

(1) 2: 1 -dimethy1- 1 :2 -thioquinocyazine iodide (prepared by fusing together l-amino-benzthiazole, 2-methylmercapto-quinoline and methylp-toluene sulphonate, extracting with pyridine and pouring into aqueous solution of potassium iodide) extends the spectral sensitivity of a silver chloride emulsion to about A 4700 A. with a maximum at about A 4350 A.

(2) 2:2'-dimethyl-thio-oxacyazine iodide (prepared in a manner similar to that of (1) except that 1-methylmercapto-benzoxazole is employed) extends the sensitivity of asilver chloride emulsion to about i. 4100 A. with a maximum at about A 3780 A.

(3) 2:2'-dimethyloxacyazine iodide (prepared by fusing together l-amino-benzoxazole methylp-toluene sulphonate and l-methylmercaptobenzoxazole methyl-p-toluene sulphonate, and pouring a solution into an aqueous solution of potassium iodide) is a weak sensitizer for silver sensitivityof'silver chloride emulsions to about A 4200 A. with a maximum at about a 4000 A.

(6) 2 :2 -dimethyl- G-benzthiocyazine iodide (prepared by fusing together l-amino ot-naphtha thiazole, l-methylmercapto" benzthiazole and methyl-p-toluene sulphonate, extracting with pyridine and pouring into an aqueous solution of potassium; iodide) extends the sensitivity of 'silver' chloride emulsions to about i. 4300 A. with a maximum at about A 4150 A.

(7) 2: 1' -dimethyl-1z4'-thioquino-cyazine iodide (prepared by-fusing together l-ethyl-quinoline-4-thione, l-amino-benzthiazole and methylp-toluene sulphonate, extracting with pyridine and pouring into an aqueous solution of potassium iodide) extends the sensitivity of silver chloride emulsions to about A 4800 A. with a maximum at about A 4500 A.

1 (8) 1:1'-dimethyl-2:2'-quinocyazine iodide isa powerful sensitizer for silver chloride emulsions,

extending the sensitivity to about A 4600 A. with sharp-maxima at about A 4150 A. and A 4400 A.

(9) 1: 1-dimethyl 2 :4 e quinocyazine iodide (prepared by condensing 2-methylmercapto-quinoline methyl-p-toluene sulphonate with -aminoquinoline methiodide in the presence of sodium ethylate) extends the sensitivity of a silver chloride emulsion to about A 4800 A. with sharp max- .ma at about i 4250 A. and 4550 A.

(10) l:1'-dimethylAW-quinocyazine iodide (prepared by condensing N-methyl-quinoline-tand.

thione methyl-p-toluene sulphonate with 4-aminoquinoline-methiodide in the presence of sodium ethylate) extends the sensitivity of a silver chloride emulsion to about A 5000 A. with a sharp maximum at about A 4550 A. and a less marked maximum at about A. 4825 A.

11) 2: 1'-dimethyl-1:2'-thiopyridocyazine iodide increases the normal sensitivity of a silver chloride emulsion and extends the range to about a 4200 A. with a maximum at about A 3025 A.

(12) 1: 1'-dimethyl-2 2'-pyridoquinocyazine iodide increases the normal sensitivity of silver chloride emulsions and extendsvthe range to about A 4300 A. with an indeterminate maximum at about i 4150 A.

, 13) 2 :2 -dimethyl-4' 5' -methylenedioxy-thioselenocyazine-p-toluene sulphonate extends the sensitivity of silver chloride emulsions to about A 4500 A. with indeterminate maxima at about A 4150 A. and i. 4300 A. i

(14) 2:3'-dimethyl-2'-methylthiol 1:4 thicpyrimidocyazine iodide increases the normal sensitivity. of silver chloride emulsions and extends the range to about a 4200 A. P

(15) 2:3'-dimethyl-1:4'-thioquinazolinocyazine N benzthiazole methiodidein pyridine solution) extendsthe sensitivity of silver chloride emulsions to about A 5200 A. with maxima at about A 4600 A.

and a 4900 A.

(1'7) 1 3 3 1'-tetramethyl-2 d' -indocarboquin- 'thiazole ethobromide and l-w-acetaniliclovinyl I ocyazine iodide (prepared by 'condensationof '4- amino quinoline methiodide and 1:3:3-trimethyl- 2-w-acetanilidovinyl indolenine iodide in the presence of sodium ethylate) extends the sensitiviiy of a silver bromide emulsion to about A 6200 with a maximum at about i. 5750 A.

(18) 1 :3 3- trlmethyl-1'- .ethyl-1:2'-indocarb0- quinocyazine-iodide (prepared in a manner simi-' lar to that of (1'7) except that 2-amino-quinoline ethiodide is employed) extends the sensitivity of a silver chloride emulsion to about A 5200 A. with maxima at about A 4950 A. and a 4550 A.

(19) 2:2'udimethylthiocyazine iodide (prepared by fusing together l-amino-benzthiazole, 1- methylmercapto-benzthiazole and methyl-p toluene sulphonate, extracting with pyridine and pouring into an aqueous solution of potassium iodide) extends the sensitivity of a silver chloride emulsion to about A 4100 A. with a maximum at about .,3050 A.

The nomenclature which I have adopted in this specification and claims may be explained as follows:

Cyazine=an alkyl salt containing two heterocyclic-rings containing a ring nitrogen atom linked by a single nitrogen atom ('N'=) in the alpha or gamma position after the manner shown in the above formulae.

-Cyadiazine=an allzyl salt containing two heterocyclic rings containing a ring nitrogen. atom linked by the chain N=CH-N= in the alpha or gamma position after the manner shown in the above formulae. s

Garbocyazine=an alkylv salt containing two heterocyclic rings containing a ring nitrogen atom linked by the chain CH=CHN= in the alpha or gamnm position after the manner shown in l the nucleus attached tothe nitrogenatom precedes the term "cyazine.

I claim:

1 A photographic silver chloride emulsion in which is incorporated as a sensitizer. a salt of the class consisting of cyazine, cyadiazine and carbo'cyazine.

2. A photographic silver chloride emulsion in which is incorporated as a sensitizer a cyazine 5 salt.

3. A photographic silver chloride emulsion in which is incorporated as a sensitizer a carbocyazine salt.

4. A photographic silver chloride emulsion in which is incorporated as a sensitizer 2:1'-dimethyl-1:2'-thioquinocyazine iodide.

5. A photographic silver chloride emulsion in' which is incorporated as a sensitizer 1:1'-dimethyl-2:2'-quinocyazine iodide.

6. A photographic silver chloride emulsion in which is incorporated as a sensitizer 1:3:3-trimethyl-1'-ethyl -1:2'-indocarboquinocyazine iodide.

7. A photographic silver chloride emulsion in which is incorporated as a sensitizer a quinccyazine salt.

' JOHN DAVID KENDALL. 

